Colour photographic processes and materials



United States Patent 3,032,413 Patented May 1, 1962 Free 3,032,413 COLOUR PHOTOGRAPHIC PROCESSE AND MATERIALS Hans von Fraunhofer, 19 Fitzalan Road, Finchley, and Harry Edward Coote, 30 Queens Grove, St. Johns Wood, both of London, England No Drawing. Filed Apr. 13, 1953, Ser. No. 348,594 Claims priority, application Great Britain Mar. 2, 1952 1 Claim. (Cl. 96-3) This invention relates to colour photographic materials and processes, and especially to cinematographic processes and materials, and has for its object to provide materials and procedures which will permit the production from chromogenic camera materials commercially satisfactory duplicate-so-called dupenegatives.

The present invention can be used with either bipack or tripack chromogenic negative materials; in the process of the invention the topmost emulsion layer of the negative material is transferred to a separate material by a take-off technique. This technique is described in British specification No. 3,344/50 and elsewhere, and one example of the technique is given in that specification. As will appear hereinafter, a different take-off process is adopted for the purpose of the present invention. By printing from the top layer by takeoff, which is in effect a black and white process considerably greater latitude exists for selecting the printing process adopted for the remaining emulsion layers of the negative material, and better quality negatives can therefore be obtained.

In one method of carrying the invention into practice with a tripack material, the camera stock has three layers of silver halide emulsion, which are differentially sensitised, and contains an appropriate colour filter or filters so that on exposure in a normal camera correct colour analysis is obtained.

The topmost layer, for the purpose of the invention need not contain a colour coupler, but different colour couplers are included in the two lower layers. On development, by a take-off process described hereinafter a separate black and white negative record of the image in the top layer is obtained and the image in the top layer obliterated, whilst leaving differently coloured negative images in the two lower layers. The duplicate nega tive is then obtained by printing from the three negative images on the two materials onto a three layer material of the reversal type.

Alternatively, in this process the take-off can be arranged to produce a positive record, and the negative images remaining in the two lower layers printed to give positive records. The three positive records can then be printed onto a suitable three layer material in known way.

In the case of the bipack material, the process is gen erally similar except that after the take-off process, one image only is left upon the developed camera material.

Further features and advantages of the invention will be apparent from the following examples.

Example 1 In this form of the invention, the negative material for exposure in the camera comprises an integral tripack chromogenic film, coated on one side of a transparent base in the following order:

Blue sensitive silver halide emulsion layer with or without a yellow colour coupler Yellow colloidal silver filter layer (4) Green sensitive silver halide emulsion layer with a magenta colour coupler (3) Red sensitive silver halide emulsion layer with a cyan colour coupler (2) Colloidal silver anti-halo layer (1) Transparent base A colour coupler can be included in the top layer if required for any reason other than that of the present invention. For example, if it is desired that the original negative be usable for printing onto a conventional chromogenic positive stock, the yellow colour coupler in the top layer will enable this to be done, whilst still permitting the process of the present invention to be used.

If this facility is not required, in which case the top layer will not contain a colour coupler, then the colour couplers of the two lower layers can be selected without regard to true colour analysis but merely to secure optimum separation in the subsequent printing. By using any of the known integral masking procedures in connection with the two lower layers the colour and tone separation resulting from the colour couplers used inthe layers is considerably improved.

In using this example of the invention with a bipack material, the camera stock is prepared as follows:

Blue-green sensitive silver halide emulsion layer (4) Colloidal yellow filter layer (3) Red sensitive silver halide emulsion layer with colour coupler (2) Colloidal silver anti-halo layer (1) Transparent base In the same way as with the tripack material colour couplers can be used in the uppermost layer, as well as the lower layer, if it is desired to print straight onto a positive stock; cyan and magenta are suitable. Otherwise any suitable coupler, for example magenta or black can be used in the lower layer only. As before, known integral masking procedures can be adopted.

After exposure of the material in the camera, the film receives the normal development and processing prescribed for chromogenic materials, for example:

(1) Colour development for ten minutes at 65 F. in a solution prepared as follows:

a. Calgon 0.5 b. Cenochrome (May & Baker) or diethyl-paraphenylene diamine hydrochloride 3.0 0. Potassium carbonate 75.0 d. Potassium bromide 2.5 e. Hydroxylamine hydrochloride 1.2 7. Water to 1,000 ml.

(2) Rinse in running Water, (3) Short stop for thirty seconds in a solution made up as follows:

a. Sodium hydroxide gm 15 b. Acetic acid (glacial) ml 60 0. Water to 1,000 ml.

(4) Wash in running water for five minutes, (5) Bleach for six minutes in a solution consisting of:

Gm. a. Potassium ferricyanide 50 12. Potassium bromide 15 0. Water to 1,000 ml.

(6) Wash in running water for six minutes.

The camera material developed and processed in accordance with the above six steps is then brought into contact with take-off material which is coated with an emulsion containing sulphides of metals such as cadimium, zinc or other suitable heavy metals. A suitable emulsion for take-oil material for this purpose is made by adding to a 10% gelatine solution 40 grams of cadmium nitrate, or an equivalent proportion of another heavy metal nitrate, and mixing well. After shredding the emulsion it is washed in a 5% solution of sodium sulphide, it is warmed to give the desired viscosity and is coated onto a suitable transparent base.

The take-01f" fihn, before being brought into contact with the camera material, is passed through a solution of sodium thiosulphate to which a small quantity of sodium sulphide may be added, in the proportion of about 1 gram per litre.

. The sodium thiosulphate solution introduced into the take-off material dissolves the bleached silver salt in the top layer of the negative and by a chemical reaction releases silver ions from the halide and by the action of the thiosulphate complex with the metal sulphide in the take-off material, creates an image in the said material in silver sulphide exactly similar to the top image of the camera material, i.e. a negative image is produced from the original negative image.

We find that the contact between the two films, camera material and take-off stock, requires only from to 40 seconds to complete the required reaction so that only the image of the top layer is afiected and, thereafter, both films are passed through a normal hypo fixing solution for a few minutes, and are then washed and dried in the normal manner. Obviously, if no dye component has been incorporated in the top layer of emulsion, the bleached silver image in the top layer is, as a result of the fixing, completely obliterated.

As a result of the transfer of the top image onto another carrier as outlined by the first example of this invention, we now have two strips of negatives, one containing the green and red records in the form of two series of colour images on one carrier, while the blue record-in the form of silver sulphide images-is on another carrier.

To produce a second generation dupe negative film, the two negatives are then printed onto a material of the reversal type, and it is coated as follows:

Green sensitive silver halide emulsion layer containing a magenta colour coupler (4) Red sensitive silver halide emulsion layer containing a cyan colour coupler (3) Colloidal yellow filter layer (2.) Blue sensitive silver halide emulsion containing a yellow colour coupler (1) Transparent base The original camera film containing the green and red records is then printed onto the two upper emulsion layers of this material; a yellow filter is used to ensure wide separation of the colours, the magenta colour being converted to a red and the cyan a green. The take-off film containing the blue record images is printed onto the material through the base with blue light. After the printing operations are completed, the film is developed and processed by the usual reversal type of chromogenic procedure which is sufiiciently well known and does not require further description herein. The processing results in a series of tricolour negative images and the dupe negative thus produced possesses excellent colour and tone separation, definition and fully graded images, suitable for printing in the usual manner onto any chromogenic positive stock available on the market.

In a modification of this process the transfer of the image in the top layer of the camera material is brought about by adding a silver solvent, such as potassium thiocyanate, to the developer, and bringing the camera material and the take-off film into contact with each other during the development; about 10 grams of thiocyanate are required with the developer given above. By this method of processing and transferring, the image produced in the take-off material is a positive one. The images in the two remaining emulsion layers can then be used to produce two black and white separation positives, by producing coloured images in the layers, by the processing as described, and then printing from these coloured images, by suitably coloured light, onto panchromatic monochrome positive material. In this way, three separation black and white positive records are obtained, which can be used to produce three second generation negatives by printing them onto any commercially available chromogenic negative film.

Example 2 An alternative method in accordance with the invention involves a camera material coated on one side of the film in the following manner:

Blue sensitive layer of silver halide emulsion without a dye component (5) Soft gelatine of low melting point with a yellow filter dye (4) Green sensitive layer of silver halide emulsion without a dye component (3) Red sensitive layer of silver halide emulsion with a dye component (2) Colloidal silver anti-halo layer (1) Transparent base After exposure in the camera, the above material is processed in the same manner as specified for Example 1, and thereafter the camera film is brought into contact with the take-off film. After the image of the top layer has been transferred onto the take-off material, the camera material is immersed in. warm water to F.) when the whole of the surface image together with the soft gelatine filter layer is dissolved and washed away.

The two lower layers are then processed in the manner disclosed hereinabove, namely, the second layer is brought into contact with the take-off material and after this operation the film is passed through the hypo fixing bath which obliterates the image in the second layer. As a result of the above processing steps we are now left with three separate strips of film, one containing the blue colour values in the form a series of silver sulphide images, the other containing a series of green colour values also in silver sulphide images, and the third one containing the red colour values in the form of a series of dye images.

These three strips of separation negatives may then be used for the production of chromogenic dupe negatives by means obvious to any technician well versed in the art, or for the production of release prints by any suitable colour printing method such as the imbibition type.

Example 3 This further example involves a camera film coated as follows:

After the development and processing of the above described material substantially as outlined for Example 1, the camera material is brought into contact with two take-off films, by placing it between two such films, one in contact with the top layer of the camera material, while the other one is to be in contact with the red sensitive layer of emulsion on the reverse side of the base. On completion of the fixing and washing steps as described for Example 1 three strips of film are obtained, one strip containing the blue record values in a series of silver sulphide images, the other containing the green colour values in a series of dye images, and the third strip containing the red colour values in a series of silver sulphide images. These three negative images can then be ap propriately printed as desired, as described above.

We claim:

A process for producing negatives from a three layer photographic primary negative material including a base, a first colour sensitised silver halide emulsion outer layer on said base, a second colour sensitised silver halide emulsion second layer on said base, and a third colour sensitised silver halide emulsion second outer layer on said base, said first, second and third colours permitting three colour analysis, which comprises developing said negative material bleaching said material, bringing the first outer layer into contact with a take-elf material including a heavy metal sulphide and a thiosulphate, whereby a silver sulphide negative image of the image in said first outer layer is produced in said take-01f material, bringing the second outer layer into contact with a further take-01f material of the same character, whereby a silver sulphide negative image of the image in said second outer layer is produced in said further take-elf material.

References Cited in the file of this patent UNITED STATES PATENTS 2,140,847 Murray et al. Dec. 20, 1938 2,628,901 Duerr Feb. 17, 1953 2,679,456 Bomback May 25, 1954 10 2,689,180 Friedman Sept. 14, 1954 2,705,676 Land et al. Apr. 5, 1955 FOREIGN PATENTS 59,365 Netherlands May 16, 1947 

